src/Reactor/LLVMJIT.cpp

// Copyright 2020 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "LLVMReactor.hpp"

#include "Debug.hpp"
#include "ExecutableMemory.hpp"
#include "Routine.hpp"

// TODO(b/143539525): Eliminate when warning has been fixed.
#ifdef _MSC_VER
__pragma(warning(push))
    __pragma(warning(disable : 4146))  // unary minus operator applied to unsigned type, result still unsigned
#endif

#include "llvm/ExecutionEngine/Orc/CompileUtils.h"
#include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
#include "llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h"
#include "llvm/ExecutionEngine/SectionMemoryManager.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Transforms/InstCombine/InstCombine.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/GVN.h"

#ifdef _MSC_VER
    __pragma(warning(pop))
#endif

#if defined(_WIN64)
        extern "C" void __chkstk();
#elif defined(_WIN32)
extern "C" void _chkstk();
#endif

#ifdef __ARM_EABI__
extern "C" signed __aeabi_idivmod();
#endif

#if __has_feature(memory_sanitizer)
#	include "sanitizer/msan_interface.h"  // TODO(b/155148722): Remove when we no longer unpoison all writes.

#	include <dlfcn.h>  // dlsym()
#endif

namespace {

// JITGlobals is a singleton that holds all the immutable machine specific
// information for the host device.
class JITGlobals
{
public:
	static JITGlobals *get();

	llvm::orc::JITTargetMachineBuilder getTargetMachineBuilder(rr::Optimization::Level optLevel) const;
	const llvm::DataLayout &getDataLayout() const;
	const llvm::Triple &getTargetTriple() const;

private:
	JITGlobals(llvm::orc::JITTargetMachineBuilder &&jitTargetMachineBuilder, llvm::DataLayout &&dataLayout);

	static llvm::CodeGenOpt::Level toLLVM(rr::Optimization::Level level);

	const llvm::orc::JITTargetMachineBuilder jitTargetMachineBuilder;
	const llvm::DataLayout dataLayout;
};

JITGlobals *JITGlobals::get()
{
	static JITGlobals instance = [] {
		llvm::InitializeNativeTarget();
		llvm::InitializeNativeTargetAsmPrinter();
		llvm::InitializeNativeTargetAsmParser();

		// TODO(b/171236524): JITTargetMachineBuilder::detectHost() currently uses the target triple of the host,
		// rather than a valid triple for the current process. Once fixed, we can use that function instead.
		llvm::orc::JITTargetMachineBuilder jitTargetMachineBuilder(llvm::Triple(LLVM_DEFAULT_TARGET_TRIPLE));

		// Retrieve host CPU name and sub-target features and add them to builder.
		// Relocation model, code model and codegen opt level are kept to default values.
		llvm::StringMap<bool> cpuFeatures;
		bool ok = llvm::sys::getHostCPUFeatures(cpuFeatures);

#if defined(__i386__) || defined(__x86_64__) || \
    (defined(__linux__) && (defined(__arm__) || defined(__aarch64__)))
		ASSERT_MSG(ok, "llvm::sys::getHostCPUFeatures returned false");
#else
		(void)ok;  // getHostCPUFeatures always returns false on other platforms
#endif

		for(auto &feature : cpuFeatures)
		{
			jitTargetMachineBuilder.getFeatures().AddFeature(feature.first(), feature.second);
		}

#if LLVM_VERSION_MAJOR >= 11 /* TODO(b/165000222): Unconditional after LLVM 11 upgrade */
		jitTargetMachineBuilder.setCPU(std::string(llvm::sys::getHostCPUName()));
#else
		jitTargetMachineBuilder.setCPU(llvm::sys::getHostCPUName());
#endif

		auto dataLayout = jitTargetMachineBuilder.getDefaultDataLayoutForTarget();
		ASSERT_MSG(dataLayout, "JITTargetMachineBuilder::getDefaultDataLayoutForTarget() failed");

		return JITGlobals(std::move(jitTargetMachineBuilder), std::move(dataLayout.get()));
	}();

	return &instance;
}

llvm::orc::JITTargetMachineBuilder JITGlobals::getTargetMachineBuilder(rr::Optimization::Level optLevel) const
{
	llvm::orc::JITTargetMachineBuilder out = jitTargetMachineBuilder;
	out.setCodeGenOptLevel(toLLVM(optLevel));

	return out;
}

const llvm::DataLayout &JITGlobals::getDataLayout() const
{
	return dataLayout;
}

const llvm::Triple &JITGlobals::getTargetTriple() const
{
	return jitTargetMachineBuilder.getTargetTriple();
}

JITGlobals::JITGlobals(llvm::orc::JITTargetMachineBuilder &&jitTargetMachineBuilder, llvm::DataLayout &&dataLayout)
    : jitTargetMachineBuilder(jitTargetMachineBuilder)
    , dataLayout(dataLayout)
{
}

llvm::CodeGenOpt::Level JITGlobals::toLLVM(rr::Optimization::Level level)
{
	switch(level)
	{
		case rr::Optimization::Level::None: return llvm::CodeGenOpt::None;
		case rr::Optimization::Level::Less: return llvm::CodeGenOpt::Less;
		case rr::Optimization::Level::Default: return llvm::CodeGenOpt::Default;
		case rr::Optimization::Level::Aggressive: return llvm::CodeGenOpt::Aggressive;
		default: UNREACHABLE("Unknown Optimization Level %d", int(level));
	}
	return llvm::CodeGenOpt::Default;
}

class MemoryMapper final : public llvm::SectionMemoryManager::MemoryMapper
{
public:
	MemoryMapper() {}
	~MemoryMapper() final {}

	llvm::sys::MemoryBlock allocateMappedMemory(
	    llvm::SectionMemoryManager::AllocationPurpose purpose,
	    size_t numBytes, const llvm::sys::MemoryBlock *const nearBlock,
	    unsigned flags, std::error_code &errorCode) final
	{
		errorCode = std::error_code();

		// Round up numBytes to page size.
		size_t pageSize = rr::memoryPageSize();
		numBytes = (numBytes + pageSize - 1) & ~(pageSize - 1);

		bool need_exec =
		    purpose == llvm::SectionMemoryManager::AllocationPurpose::Code;
		void *addr = rr::allocateMemoryPages(
		    numBytes, flagsToPermissions(flags), need_exec);
		if(!addr)
			return llvm::sys::MemoryBlock();
		return llvm::sys::MemoryBlock(addr, numBytes);
	}

	std::error_code protectMappedMemory(const llvm::sys::MemoryBlock &block,
	                                    unsigned flags)
	{
		// Round down base address to align with a page boundary. This matches
		// DefaultMMapper behavior.
		void *addr = block.base();
		size_t size = block.allocatedSize();
		size_t pageSize = rr::memoryPageSize();
		addr = reinterpret_cast<void *>(
		    reinterpret_cast<uintptr_t>(addr) & ~(pageSize - 1));
		size += reinterpret_cast<uintptr_t>(block.base()) -
		        reinterpret_cast<uintptr_t>(addr);

		rr::protectMemoryPages(addr, size, flagsToPermissions(flags));
		return std::error_code();
	}

	std::error_code releaseMappedMemory(llvm::sys::MemoryBlock &block)
	{
		size_t size = block.allocatedSize();

		rr::deallocateMemoryPages(block.base(), size);
		return std::error_code();
	}

private:
	int flagsToPermissions(unsigned flags)
	{
		int result = 0;
		if(flags & llvm::sys::Memory::MF_READ)
		{
			result |= rr::PERMISSION_READ;
		}
		if(flags & llvm::sys::Memory::MF_WRITE)
		{
			result |= rr::PERMISSION_WRITE;
		}
		if(flags & llvm::sys::Memory::MF_EXEC)
		{
			result |= rr::PERMISSION_EXECUTE;
		}
		return result;
	}
};

template<typename T>
T alignUp(T val, T alignment)
{
	return alignment * ((val + alignment - 1) / alignment);
}

void *alignedAlloc(size_t size, size_t alignment)
{
	ASSERT(alignment < 256);
	auto allocation = new uint8_t[size + sizeof(uint8_t) + alignment];
	auto aligned = allocation;
	aligned += sizeof(uint8_t);                                                                       // Make space for the base-address offset.
	aligned = reinterpret_cast<uint8_t *>(alignUp(reinterpret_cast<uintptr_t>(aligned), alignment));  // align
	auto offset = static_cast<uint8_t>(aligned - allocation);
	aligned[-1] = offset;
	return aligned;
}

void alignedFree(void *ptr)
{
	auto aligned = reinterpret_cast<uint8_t *>(ptr);
	auto offset = aligned[-1];
	auto allocation = aligned - offset;
	delete[] allocation;
}

template<typename T>
static void atomicLoad(void *ptr, void *ret, llvm::AtomicOrdering ordering)
{
	*reinterpret_cast<T *>(ret) = std::atomic_load_explicit<T>(reinterpret_cast<std::atomic<T> *>(ptr), rr::atomicOrdering(ordering));
}

template<typename T>
static void atomicStore(void *ptr, void *val, llvm::AtomicOrdering ordering)
{
	std::atomic_store_explicit<T>(reinterpret_cast<std::atomic<T> *>(ptr), *reinterpret_cast<T *>(val), rr::atomicOrdering(ordering));
}

#ifdef __ANDROID__
template<typename F>
static uint32_t sync_fetch_and_op(uint32_t volatile *ptr, uint32_t val, F f)
{
	// Build an arbitrary op out of looped CAS
	for(;;)
	{
		uint32_t expected = *ptr;
		uint32_t desired = f(expected, val);

		if(expected == __sync_val_compare_and_swap_4(ptr, expected, desired))
		{
			return expected;
		}
	}
}
#endif

#if LLVM_VERSION_MAJOR >= 11 /* TODO(b/165000222): Unconditional after LLVM 11 upgrade */
class ExternalSymbolGenerator : public llvm::orc::DefinitionGenerator
#else
class ExternalSymbolGenerator : public llvm::orc::JITDylib::DefinitionGenerator
#endif
{
	struct Atomic
	{
		static void load(size_t size, void *ptr, void *ret, llvm::AtomicOrdering ordering)
		{
			switch(size)
			{
				case 1: atomicLoad<uint8_t>(ptr, ret, ordering); break;
				case 2: atomicLoad<uint16_t>(ptr, ret, ordering); break;
				case 4: atomicLoad<uint32_t>(ptr, ret, ordering); break;
				case 8: atomicLoad<uint64_t>(ptr, ret, ordering); break;
				default:
					UNIMPLEMENTED_NO_BUG("Atomic::load(size: %d)", int(size));
			}
		}
		static void store(size_t size, void *ptr, void *ret, llvm::AtomicOrdering ordering)
		{
			switch(size)
			{
				case 1: atomicStore<uint8_t>(ptr, ret, ordering); break;
				case 2: atomicStore<uint16_t>(ptr, ret, ordering); break;
				case 4: atomicStore<uint32_t>(ptr, ret, ordering); break;
				case 8: atomicStore<uint64_t>(ptr, ret, ordering); break;
				default:
					UNIMPLEMENTED_NO_BUG("Atomic::store(size: %d)", int(size));
			}
		}
	};

	static void nop() {}
	static void neverCalled() { UNREACHABLE("Should never be called"); }

	static void *coroutine_alloc_frame(size_t size) { return alignedAlloc(size, 16); }
	static void coroutine_free_frame(void *ptr) { alignedFree(ptr); }

#ifdef __ANDROID__
	// forwarders since we can't take address of builtins
	static void sync_synchronize() { __sync_synchronize(); }
	static uint32_t sync_fetch_and_add_4(uint32_t *ptr, uint32_t val) { return __sync_fetch_and_add_4(ptr, val); }
	static uint32_t sync_fetch_and_and_4(uint32_t *ptr, uint32_t val) { return __sync_fetch_and_and_4(ptr, val); }
	static uint32_t sync_fetch_and_or_4(uint32_t *ptr, uint32_t val) { return __sync_fetch_and_or_4(ptr, val); }
	static uint32_t sync_fetch_and_xor_4(uint32_t *ptr, uint32_t val) { return __sync_fetch_and_xor_4(ptr, val); }
	static uint32_t sync_fetch_and_sub_4(uint32_t *ptr, uint32_t val) { return __sync_fetch_and_sub_4(ptr, val); }
	static uint32_t sync_lock_test_and_set_4(uint32_t *ptr, uint32_t val) { return __sync_lock_test_and_set_4(ptr, val); }
	static uint32_t sync_val_compare_and_swap_4(uint32_t *ptr, uint32_t expected, uint32_t desired) { return __sync_val_compare_and_swap_4(ptr, expected, desired); }

	static uint32_t sync_fetch_and_max_4(uint32_t *ptr, uint32_t val)
	{
		return sync_fetch_and_op(ptr, val, [](int32_t a, int32_t b) { return std::max(a, b); });
	}
	static uint32_t sync_fetch_and_min_4(uint32_t *ptr, uint32_t val)
	{
		return sync_fetch_and_op(ptr, val, [](int32_t a, int32_t b) { return std::min(a, b); });
	}
	static uint32_t sync_fetch_and_umax_4(uint32_t *ptr, uint32_t val)
	{
		return sync_fetch_and_op(ptr, val, [](uint32_t a, uint32_t b) { return std::max(a, b); });
	}
	static uint32_t sync_fetch_and_umin_4(uint32_t *ptr, uint32_t val)
	{
		return sync_fetch_and_op(ptr, val, [](uint32_t a, uint32_t b) { return std::min(a, b); });
	}
#endif

	class Resolver
	{
	public:
		using FunctionMap = llvm::StringMap<void *>;

		FunctionMap functions;

		Resolver()
		{
#ifdef ENABLE_RR_PRINT
			functions.try_emplace("rr::DebugPrintf", reinterpret_cast<void *>(rr::DebugPrintf));
#endif
			functions.try_emplace("nop", reinterpret_cast<void *>(nop));
			functions.try_emplace("floorf", reinterpret_cast<void *>(floorf));
			functions.try_emplace("nearbyintf", reinterpret_cast<void *>(nearbyintf));
			functions.try_emplace("truncf", reinterpret_cast<void *>(truncf));
			functions.try_emplace("printf", reinterpret_cast<void *>(printf));
			functions.try_emplace("puts", reinterpret_cast<void *>(puts));
			functions.try_emplace("fmodf", reinterpret_cast<void *>(fmodf));

			functions.try_emplace("sinf", reinterpret_cast<void *>(sinf));
			functions.try_emplace("cosf", reinterpret_cast<void *>(cosf));
			functions.try_emplace("asinf", reinterpret_cast<void *>(asinf));
			functions.try_emplace("acosf", reinterpret_cast<void *>(acosf));
			functions.try_emplace("atanf", reinterpret_cast<void *>(atanf));
			functions.try_emplace("sinhf", reinterpret_cast<void *>(sinhf));
			functions.try_emplace("coshf", reinterpret_cast<void *>(coshf));
			functions.try_emplace("tanhf", reinterpret_cast<void *>(tanhf));
			functions.try_emplace("asinhf", reinterpret_cast<void *>(asinhf));
			functions.try_emplace("acoshf", reinterpret_cast<void *>(acoshf));
			functions.try_emplace("atanhf", reinterpret_cast<void *>(atanhf));
			functions.try_emplace("atan2f", reinterpret_cast<void *>(atan2f));
			functions.try_emplace("powf", reinterpret_cast<void *>(powf));
			functions.try_emplace("expf", reinterpret_cast<void *>(expf));
			functions.try_emplace("logf", reinterpret_cast<void *>(logf));
			functions.try_emplace("exp2f", reinterpret_cast<void *>(exp2f));
			functions.try_emplace("log2f", reinterpret_cast<void *>(log2f));

			functions.try_emplace("sin", reinterpret_cast<void *>(static_cast<double (*)(double)>(sin)));
			functions.try_emplace("cos", reinterpret_cast<void *>(static_cast<double (*)(double)>(cos)));
			functions.try_emplace("asin", reinterpret_cast<void *>(static_cast<double (*)(double)>(asin)));
			functions.try_emplace("acos", reinterpret_cast<void *>(static_cast<double (*)(double)>(acos)));
			functions.try_emplace("atan", reinterpret_cast<void *>(static_cast<double (*)(double)>(atan)));
			functions.try_emplace("sinh", reinterpret_cast<void *>(static_cast<double (*)(double)>(sinh)));
			functions.try_emplace("cosh", reinterpret_cast<void *>(static_cast<double (*)(double)>(cosh)));
			functions.try_emplace("tanh", reinterpret_cast<void *>(static_cast<double (*)(double)>(tanh)));
			functions.try_emplace("asinh", reinterpret_cast<void *>(static_cast<double (*)(double)>(asinh)));
			functions.try_emplace("acosh", reinterpret_cast<void *>(static_cast<double (*)(double)>(acosh)));
			functions.try_emplace("atanh", reinterpret_cast<void *>(static_cast<double (*)(double)>(atanh)));
			functions.try_emplace("atan2", reinterpret_cast<void *>(static_cast<double (*)(double, double)>(atan2)));
			functions.try_emplace("pow", reinterpret_cast<void *>(static_cast<double (*)(double, double)>(pow)));
			functions.try_emplace("exp", reinterpret_cast<void *>(static_cast<double (*)(double)>(exp)));
			functions.try_emplace("log", reinterpret_cast<void *>(static_cast<double (*)(double)>(log)));
			functions.try_emplace("exp2", reinterpret_cast<void *>(static_cast<double (*)(double)>(exp2)));
			functions.try_emplace("log2", reinterpret_cast<void *>(static_cast<double (*)(double)>(log2)));

			functions.try_emplace("atomic_load", reinterpret_cast<void *>(Atomic::load));
			functions.try_emplace("atomic_store", reinterpret_cast<void *>(Atomic::store));

			// FIXME(b/119409619): use an allocator here so we can control all memory allocations
			functions.try_emplace("coroutine_alloc_frame", reinterpret_cast<void *>(coroutine_alloc_frame));
			functions.try_emplace("coroutine_free_frame", reinterpret_cast<void *>(coroutine_free_frame));

#ifdef __APPLE__
			functions.try_emplace("sincosf_stret", reinterpret_cast<void *>(__sincosf_stret));
#elif defined(__linux__)
			functions.try_emplace("sincosf", reinterpret_cast<void *>(sincosf));
#elif defined(_WIN64)
			functions.try_emplace("chkstk", reinterpret_cast<void *>(__chkstk));
#elif defined(_WIN32)
			functions.try_emplace("chkstk", reinterpret_cast<void *>(_chkstk));
#endif

#ifdef __ARM_EABI__
			functions.try_emplace("aeabi_idivmod", reinterpret_cast<void *>(__aeabi_idivmod));
#endif
#ifdef __ANDROID__
			functions.try_emplace("aeabi_unwind_cpp_pr0", reinterpret_cast<void *>(neverCalled));
			functions.try_emplace("sync_synchronize", reinterpret_cast<void *>(sync_synchronize));
			functions.try_emplace("sync_fetch_and_add_4", reinterpret_cast<void *>(sync_fetch_and_add_4));
			functions.try_emplace("sync_fetch_and_and_4", reinterpret_cast<void *>(sync_fetch_and_and_4));
			functions.try_emplace("sync_fetch_and_or_4", reinterpret_cast<void *>(sync_fetch_and_or_4));
			functions.try_emplace("sync_fetch_and_xor_4", reinterpret_cast<void *>(sync_fetch_and_xor_4));
			functions.try_emplace("sync_fetch_and_sub_4", reinterpret_cast<void *>(sync_fetch_and_sub_4));
			functions.try_emplace("sync_lock_test_and_set_4", reinterpret_cast<void *>(sync_lock_test_and_set_4));
			functions.try_emplace("sync_val_compare_and_swap_4", reinterpret_cast<void *>(sync_val_compare_and_swap_4));
			functions.try_emplace("sync_fetch_and_max_4", reinterpret_cast<void *>(sync_fetch_and_max_4));
			functions.try_emplace("sync_fetch_and_min_4", reinterpret_cast<void *>(sync_fetch_and_min_4));
			functions.try_emplace("sync_fetch_and_umax_4", reinterpret_cast<void *>(sync_fetch_and_umax_4));
			functions.try_emplace("sync_fetch_and_umin_4", reinterpret_cast<void *>(sync_fetch_and_umin_4));
#endif
#if __has_feature(memory_sanitizer)
			functions.try_emplace("msan_unpoison", reinterpret_cast<void *>(__msan_unpoison));  // TODO(b/155148722): Remove when we no longer unpoison all writes.
#endif
		}
	};

	llvm::Error tryToGenerate(
#if LLVM_VERSION_MAJOR >= 11 /* TODO(b/165000222): Unconditional after LLVM 11 upgrade */
	    llvm::orc::LookupState &state,
#endif
	    llvm::orc::LookupKind kind,
	    llvm::orc::JITDylib &dylib,
	    llvm::orc::JITDylibLookupFlags flags,
	    const llvm::orc::SymbolLookupSet &set) override
	{
		static Resolver resolver;

		llvm::orc::SymbolMap symbols;

#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
		std::string missing;
#endif  // !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)

		for(auto symbol : set)
		{
			auto name = symbol.first;

			// Trim off any underscores from the start of the symbol. LLVM likes
			// to append these on macOS.
			auto trimmed = (*name).drop_while([](char c) { return c == '_'; });

			auto it = resolver.functions.find(trimmed.str());
			if(it != resolver.functions.end())
			{
				symbols[name] = llvm::JITEvaluatedSymbol(
				    static_cast<llvm::JITTargetAddress>(reinterpret_cast<uintptr_t>(it->second)),
				    llvm::JITSymbolFlags::Exported);

				continue;
			}

#if __has_feature(memory_sanitizer)
			// MemorySanitizer uses a dynamically linked runtime. Instrumented routines reference
			// some symbols from this library. Look them up dynamically in the default namespace.
			// Note this approach should not be used for other symbols, since they might not be
			// visible (e.g. due to static linking), we may wish to provide an alternate
			// implementation, and/or it would be a security vulnerability.

			void *address = dlsym(RTLD_DEFAULT, (*symbol.first).data());

			if(address)
			{
				symbols[name] = llvm::JITEvaluatedSymbol(
				    static_cast<llvm::JITTargetAddress>(reinterpret_cast<uintptr_t>(address)),
				    llvm::JITSymbolFlags::Exported);

				continue;
			}
#endif

#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
			missing += (missing.empty() ? "'" : ", '") + (*name).str() + "'";
#endif
		}

#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
		// Missing functions will likely make the module fail in non-obvious ways.
		if(!missing.empty())
		{
			WARN("Missing external functions: %s", missing.c_str());
		}
#endif

		if(symbols.empty())
		{
			return llvm::Error::success();
		}

		return dylib.define(llvm::orc::absoluteSymbols(std::move(symbols)));
	}
};

// As we must support different LLVM versions, add a generic Unwrap for functions that return Expected<T> or the actual T.
// TODO(b/165000222): Remove after LLVM 11 upgrade
template<typename T>
auto &Unwrap(llvm::Expected<T> &&v)
{
	return v.get();
}
template<typename T>
auto &Unwrap(T &&v)
{
	return v;
}

// JITRoutine is a rr::Routine that holds a LLVM JIT session, compiler and
// object layer as each routine may require different target machine
// settings and no Reactor routine directly links against another.
class JITRoutine : public rr::Routine
{
	llvm::orc::ExecutionSession session;
	llvm::orc::RTDyldObjectLinkingLayer objectLayer;
	llvm::orc::IRCompileLayer compileLayer;
	llvm::orc::MangleAndInterner mangle;
	llvm::orc::ThreadSafeContext ctx;
	llvm::orc::JITDylib &dylib;
	std::vector<const void *> addresses;

public:
	JITRoutine(
	    std::unique_ptr<llvm::Module> module,
	    llvm::Function **funcs,
	    size_t count,
	    const rr::Config &config)
	    : objectLayer(session, []() {
		    static MemoryMapper memoryMapper;
		    return std::make_unique<llvm::SectionMemoryManager>(&memoryMapper);
	    })
	    , compileLayer(session, objectLayer, std::make_unique<llvm::orc::ConcurrentIRCompiler>(JITGlobals::get()->getTargetMachineBuilder(config.getOptimization().getLevel())))
	    , mangle(session, JITGlobals::get()->getDataLayout())
	    , ctx(std::make_unique<llvm::LLVMContext>())
	    , dylib(Unwrap(session.createJITDylib("<routine>")))
	    , addresses(count)
	{

#ifdef ENABLE_RR_DEBUG_INFO
		// TODO(b/165000222): Update this on next LLVM roll.
		// https://github.com/llvm/llvm-project/commit/98f2bb4461072347dcca7d2b1b9571b3a6525801
		// introduces RTDyldObjectLinkingLayer::registerJITEventListener().
		// The current API does not appear to have any way to bind the
		// rr::DebugInfo::NotifyFreeingObject event.
		objectLayer.setNotifyLoaded([](llvm::orc::VModuleKey,
		                               const llvm::object::ObjectFile &obj,
		                               const llvm::RuntimeDyld::LoadedObjectInfo &l) {
			static std::atomic<uint64_t> unique_key{ 0 };
			rr::DebugInfo::NotifyObjectEmitted(unique_key++, obj, l);
		});
#endif  // ENABLE_RR_DEBUG_INFO

		if(JITGlobals::get()->getTargetTriple().isOSBinFormatCOFF())
		{
			// Hack to support symbol visibility in COFF.
			// Matches hack in llvm::orc::LLJIT::createObjectLinkingLayer().
			// See documentation on these functions for more detail.
			objectLayer.setOverrideObjectFlagsWithResponsibilityFlags(true);
			objectLayer.setAutoClaimResponsibilityForObjectSymbols(true);
		}

		dylib.addGenerator(std::make_unique<ExternalSymbolGenerator>());

		llvm::SmallVector<llvm::orc::SymbolStringPtr, 8> names(count);
		for(size_t i = 0; i < count; i++)
		{
			auto func = funcs[i];
			func->setLinkage(llvm::GlobalValue::ExternalLinkage);
			func->setDoesNotThrow();
			if(!func->hasName())
			{
				func->setName("f" + llvm::Twine(i).str());
			}
			names[i] = mangle(func->getName());
		}

		// Once the module is passed to the compileLayer, the
		// llvm::Functions are freed. Make sure funcs are not referenced
		// after this point.
		funcs = nullptr;

		llvm::cantFail(compileLayer.add(dylib, llvm::orc::ThreadSafeModule(std::move(module), ctx)));

		// Resolve the function addresses.
		for(size_t i = 0; i < count; i++)
		{
			auto symbol = session.lookup({ &dylib }, names[i]);
			ASSERT_MSG(symbol, "Failed to lookup address of routine function %d: %s",
			           (int)i, llvm::toString(symbol.takeError()).c_str());
			addresses[i] = reinterpret_cast<void *>(static_cast<intptr_t>(symbol->getAddress()));
		}
	}

	~JITRoutine()
	{
#if LLVM_VERSION_MAJOR >= 11 /* TODO(b/165000222): Unconditional after LLVM 11 upgrade */
		if(auto err = session.endSession())
		{
			session.reportError(std::move(err));
		}
#endif
	}

	const void *getEntry(int index) const override
	{
		return addresses[index];
	}
};

}  // anonymous namespace

namespace rr {

JITBuilder::JITBuilder(const rr::Config &config)
    : config(config)
    , module(new llvm::Module("", context))
    , builder(new llvm::IRBuilder<>(context))
{
	module->setTargetTriple(LLVM_DEFAULT_TARGET_TRIPLE);
	module->setDataLayout(JITGlobals::get()->getDataLayout());
}

void JITBuilder::optimize(const rr::Config &cfg)
{
#ifdef ENABLE_RR_DEBUG_INFO
	if(debugInfo != nullptr)
	{
		return;  // Don't optimize if we're generating debug info.
	}
#endif  // ENABLE_RR_DEBUG_INFO

	llvm::legacy::PassManager passManager;

	for(auto pass : cfg.getOptimization().getPasses())
	{
		switch(pass)
		{
			case rr::Optimization::Pass::Disabled: break;
			case rr::Optimization::Pass::CFGSimplification: passManager.add(llvm::createCFGSimplificationPass()); break;
			case rr::Optimization::Pass::LICM: passManager.add(llvm::createLICMPass()); break;
			case rr::Optimization::Pass::AggressiveDCE: passManager.add(llvm::createAggressiveDCEPass()); break;
			case rr::Optimization::Pass::GVN: passManager.add(llvm::createGVNPass()); break;
			case rr::Optimization::Pass::InstructionCombining: passManager.add(llvm::createInstructionCombiningPass()); break;
			case rr::Optimization::Pass::Reassociate: passManager.add(llvm::createReassociatePass()); break;
			case rr::Optimization::Pass::DeadStoreElimination: passManager.add(llvm::createDeadStoreEliminationPass()); break;
			case rr::Optimization::Pass::SCCP: passManager.add(llvm::createSCCPPass()); break;
			case rr::Optimization::Pass::ScalarReplAggregates: passManager.add(llvm::createSROAPass()); break;
			case rr::Optimization::Pass::EarlyCSEPass: passManager.add(llvm::createEarlyCSEPass()); break;
			default:
				UNREACHABLE("pass: %d", int(pass));
		}
	}

	passManager.run(*module);
}

std::shared_ptr<rr::Routine> JITBuilder::acquireRoutine(llvm::Function **funcs, size_t count, const rr::Config &cfg)
{
	ASSERT(module);
	return std::make_shared<JITRoutine>(std::move(module), funcs, count, cfg);
}

}  // namespace rr